Worst-case scenario: Research finds 50% of world’s coral reefs face death by 2035

Half of the world’s coral reefs will face death and other marine life will struggle to survive because of a disruption in the food chain by 2035 if climate change continues its unrelenting assault on ocean ecosystems.

That’s the worst-case scenario in findings by researchers at the University of Hawaiʻi at Mānoa that were published this month in PLOS Biology.

“While the negative impacts of climate change on coral reefs are well known, this research shows that they are actually worse than anticipated due to a broad combination of climate change-induced stressors,” the study’s lead author Renee O. Setter, a doctoral student in the Department of Geography and Environment in UH-Mānoa’s College of Social Sciences, said in a press release. “It was surprising to find that so many global coral reefs would be overwhelmed by unsuitable environmental conditions so soon due to multiple stressors.”

Setter and his team used several global climate change models to compare scenarios of five environmental stressors projected from the 1950s through 2100 that could lead to unsuitable environmental conditions for coral reefs. Stressors included sea surface temperature, ocean acidification, tropical storms, land use and human population.

The team’s key findings included:

• In 2035, 50% of the world’s coral reefs will be unsuitable when multiple stressors are considered. For example, one region could be experiencing higher sea surface temperature while another region might be experiencing ocean acidification. If only an individual stressor is considered, fewer areas seem to be impacted as quickly and the date is pushed back to 2050.
• By 2055, it is projected almost all of the world’s coral reefs, or 99%, will face unsuitable conditions based on at least one of the five stressors studied.
• By 2100, it is anticipated that 93% of global reefs would be under threat by two or more stressors.

“We know that corals are vulnerable to increasing sea surface temperatures and marine heat waves due to climate change. But it is important to include the complete anthropogenic (environmental change caused or influenced by human activity) impact from numerous stressors that coral reefs are exposed to in order to get a better sense of the overall risks to these ecosystems,” one of the study’s co-authors Erik Franklin, associate research professor at the Hawaiʻi Institute of Marine Biology in UH-Manoa’s School of Ocean and Earth Sciences and Technology, said in the press release. “This has great implications for our local Hawaiian reefs that are key to local biodiversity, island culture, fisheries and tourism.”

According to researchers, this study is the first that looks at multiple stressors in modeling and projection scenarios to show that the cumulative area impacted by any stressor is leading to a greater coverage of unsuitable conditions globally. This is creating a shorter timeline for remaining reefs, as they can be vulnerable to one of many projected stressors that are quickly approaching.

The research team’s next phase will take a closer look at how climate change is projected to affect individual coral species.